Six major wildfires burning in California

More than 3000 firefighters are battling six major wildfires in California, the state fire agency says.

One of the fiercest fires has shut the Pacific Coast Highway for the second time in as many days, with a 50km stretch off-limits.

The so-called Springs fire has reached the coast north-west of Los Angeles, threatening thousands of homes. It has tripled in size since Friday morning, burning nearly 70 square kilometres a day after breaking out near Camarillo.

It has damaged more than a dozen homes, with another 4000 at risk. No injuries have been reported but hundreds of homes and a military base have been evacuated, and a university campus has closed.

Residents were told to leave more than 900 homes in Hidden Valley, an enclave of ranches and estate-type properties south-east of Camarillo. About 200 dwellings were evacuated earlier along the coastal highway and adjacent canyon roads.

Fire managers said they expected it would take until Monday to fully contain the fire.

The outbreak of brushfires and wildfires marked a fierce start to a fire season in California that weather forecasters predict will be worsened by a summer of high temperatures and drought throughout much of the US West.

Fire crews have tackled more than 680 wildfires so far this year, about 200 more than average for the period.